Is your feature request related to a problem? Please describe.

We would like to be able to rename services through configuration with the service mapping env var. This is something we are able to do in Java, Python, etc. but not in Ruby.

In the additional configuration section, we see other env vars that can change the default behavior of Datadog tracing, but service mapping is missing.

Describe the goal of the feature

This is the description from the Configuring the Java Tracing Library page:
Example: mysql:my-mysql-service-name-db, postgres:my-postgres-service-name-db
Dynamically rename services via configuration. Useful for making databases have distinct names across different services.

And from Python:
Define service name mappings to allow renaming services in traces, for example: postgres:postgresql,defaultdb:postgresql.

Additional context

Here's the request and PR from Java where this was addressed:
DataDog/dd-trace-java#65
DataDog/dd-trace-java#314

And from Python:
DataDog/dd-trace-py#897
DataDog/dd-trace-py#2031